A perianal subcutaneous metastasis as the presenting sign for lung cancer

Metastases to soft tissues are rarely reported in the initial presentation and diagnosis of lung cancer. We report a case of a 77-year-old white man who presented with a 9-day history of a painful, rapidly growing mass on his left buttock in the gluteal cleft. The deep dermal location of the neoplasm and the lack of epidermal involvement led to suspicion of a metastatic carcinoma. Imaging showed a lung lesion suspected to be a primary malignancy with distant liver and gastric fundus metastases. Lung pathology showed primarily adenocarcinoma with squamous differentiation, whereas the skin biopsy showed poorly differentiated squamous cell carcinoma. Clinically, we concluded the skin carcinoma was a metastasis of a primary lung adenocarcinoma with squamous differentiation. This case highlights the importance of appropriate preventative screening.